purchasing a nailing fin

Does anyone have any ideas on how I can find a nailing fin to fit into the fin groove on a replacement vinyl window? I have called the manufacturer (Dove), but they are not geting back to me and they sell only to dealers and there are no Dove dealers in the Northeast. I looked in HomeDepot and the fins they sell are made to fit American Craftsman windows, not the one I have. I am stumped! Any ideas would be very helpful!